There are available various types of construction for a rotary head assembly of a VTR. For example, a basic type is constructed of two cylindrical bodies (hereinafter called cylinder) having nearly equal ODs which are arranged coaxially with each other.
FIG. 1 shows an example of the structure of a conventional rotary head assembly. Referring to FIG. 1, 1 denotes a rotary shaft, which is rotatably supported by bearings 2 and 3 which is rotationally driven by a driving motor (not shown in this figure). Magnetic head 4 is secured on the rotary shaft 1 through a member 5, to be rotated at a specified speed. Upper fixed cylinder 6 is bound coaxially to lower fixed cylinder 8 through a member 7 and the lower fixed cylinder 8 is, in turn, secured in position on a base of the VTR. Numerals 9 and 10 designate collars or sleeves and 11 a bearing retaining ring. The structure of the conventional rotary head assembly such as shown in FIG. 1 has defects as described hereunder:
(1) It is difficult to align the axial center of the upper fixed cylinder and that of the lower fixed cylinder at a desired accuracy.
(2) In the small rotary head assembly which is employed in a 8 mm type portable video camera having a camera and video tape recorder combined as a single unit, its cylinder diameter is reduced to about 2/3, and the magnetic tape width to 1/2, as compared with a conventional video rotary head assembly utilizing a 1/2 inch width magnetic tape, but its rotational speed is still the same as the conventional speed of 1,800 rpm. For this reason, in order to have an adequate running distance of the magnetic head on the magnetic tape per one TV picture frame, the angle that the running surface of the magnetic head makes with the running direction of the magnetic tape needs to be reduced from that in the conventional assembly. To effect this, the angle at which the magnetic tape is wound on the cylinders, which is approx. 190.degree. in the case of the conventional 1/2 inch tape must be increased to approx. 220.degree. in the 8 mm type camera. This makes impractical the upper cylinder fixing method such as shown in FIG. 1.